1. Field of the Invention
The present invention relates to a hose connecting assembly and, in particular, one used for connecting a hose to a fitting, for connecting together several hoses or forming branched connections using two or more hoses.
2. Background Information
A hose connecting assembly, used for a branch connection, is described in Japanese Unexamined Patent Publication Tokkai-Sho 62-233591 and 62-233592, which correspond to U.S. Pat. No. 5,033,775. As shown in FIG. 12, the hose connecting assembly comprises a T-shaped connecting tube 100 which allows three hoses 201, 202 and 203 to be connected to one another in three directions. A plastic cover 300 extends around the whole connection. In order to assemble this hose connecting assembly, each connecting portion of tube 100 is inserted into hoses 201, 202 and 203 respectively. Thereafter, each connecting portion of tube 100 is placed in a mold and a reinforced polyamide resin cover 300 is formed about the exterior of the tube and connection hose. Since the resin cover 300 is shrunk at a shrinkage factor of 1% or more as it solidifies, a sufficient diameter reducing force is applied upon the surface of each of the hoses. This causes each hose to be nipped between cover 300 and the respective portion of connecting tube 100 to provide a high sealing pressure. A similar hose connecting assembly is disclosed in U.S. Pat. No. 4,997,213.
Such hose connecting assemblies permit the creation of high sealing pressures by a simple method. However, since the presence of residual stress in the formed resin cover may be high if the thermal shrinkage factor in the fiber reinforced polyamide resin is as high as not less than 1%, stress cracking may occur in the cover due to the accumulation of road salt. This was shown by an experiment in which the hose connecting assembly was immersed in a high concentration zinc chloride.
The present inventors have found that the stress cracks have specific properties in position where they occur. That is, the stress cracks readily occur particularly at welds which are formed on molding.